Branchial Organs of the hifuso^ia. 55 



current till it is again attracted, and swallowed in its turn. 

 Sometimes these animals put their turning machines in motion 

 when they are not hungry, and then tlie whole of the nutritive 

 particles are repelled. 



Cuvier, on this point, seems to have adopted the opinion of 

 the accurate and distinguished observer, M. Savigny, who had 

 compared the basis of the wheels with the branchial sacs of 

 the ascidies. But it is evident that the analogy vrhich he sup- 

 poses to exist between these two is erroneous in many particu- 

 lars ; and Schweigger, in his Manual, opposes himself to this 

 explanation of the functions of the rotatory organs, because it 

 presupposes the existence of a sanguineous circulation which 

 does not exist. He considers them as organs destined for seiz- 

 ing the food, although he does not refute the reasons against 

 this opinion adduced by Schrank. M. Bory de St Vincent (in 

 the Diet. Classique d'Hist. Naturelle, Art. Rotifere) states these 

 organs to be the respiratory organs, without, however, support- 

 ing his opinion on any accurate researches. He affirms that, with- 

 out doubt, the Rotatoria have a circulation, because they have 

 a heart, and that the rotatory organs are analogous to the bran- 

 chial apparatus of other animals. His expressions on this point 

 are very decided ; but the organ which M. Bory de St Vincent has 

 taken for the heart is the pharynx, or rather the vibratory canal 

 which leads from the middle portion of the base of the rotatory 

 organs, situated upon the ventral side of the animal, to the pha- 

 rynx, and which forms the cavity of the mouth, properly so 

 called. This is proved by the fact, that when these Infusores 

 are fed with indigo, this vibratory portion forms a continued 

 line of a blue colour, indicating the passage to the pharynx. 

 We may add, that the whole of the reasoning of this author is 

 founded upon this erroneous observation. 



On the other hand, another observer, very fortunate and very 

 accurate, Mr Carus, has proved, according to his philosophical 

 method of demonstration, the existence of respiration not only in 

 the Rotifera but also in all the rotatory infusores. He thus ex- 

 presses himself on the subject in his dissertation upon the develop- 

 ment of the bivalves of fresh water. (Nova Acta Natur. Curios, 

 xvi. 1831). '* All the external parts of locomotion have invariably 

 as their starting point — their necessary foundation— «a respiratory 



